The commit would look exactly like that if it was a 100% deterministic transpilation (like Golang did with their original C implementation?).

This is obviously very different from that, but the way the commit looks doesn't make it so.

The question isn't whether or not you'd get the same line count with a non-LLM tool. The question of whether or not it's vibe-coded depends on whether or not the committer actually reviewed and understood the new code. And with a 75k line difference, that seems unlikely.